Frankenscope? Let's see it!***be advised that NOTHING in this forum has been safety tested and you are reading and using these posts at your own peril. blah, blah, blah... dont mess around with your eyesight when it comes to solar astronomy. Use appropriate filtration at all times...

Andover has announced a new series of hard-coated narrow band filters:

Andover filters.jpg (104.34 KiB) Viewed 2226 times

ANDOVER CORPORATION'S Hard-Coated Narrowband Optical Filters are designed to perform at the highest level for the most demanding applications. Boasting peak transmission as high as 98%, these filters feature excellent throughput while providing dense out-of-band blocking. Available in wavelengths from 334nm to 1550nm, including all major laser and atomic absorption lines. All filters are mounted in black-anodized aluminum rings to provide protection and easy identification.

These ~ 21 mm clear diameter filters are housed in a 25 mm anodized filter cell, and are stated to be "suitable for high temperature applications" (up to 200 C) since they do not use absorbing substrates. Most are OD 4 blocked from 300 to 1200 nm, with a bandpass of 10 nm. The only down side is that they are listed as having a flatness of 3-5 waves, which means they must be located fairly close to focus so as to not introduce optical aberrations. Nonetheless, they would appear to be very suitable for ERF/blocking filter components at the near-the-focal-plane location.

They have specific filters for CaK @ 394 nm and H alpha @ 656 nm. Both are $180 USD.

Hi,Bob-
I am interested to see if they can make a bf10 blocking filter that I can swap the bf5 out of my PST. I e-mailed them. I asked them if they ever did a PST mod. like this before. I would prefer not to buy the bf10 blocking filter/diagonal at $500,so we'll see.
Robert

These filters - specifically the H alpha filter - would not be a suitable replacement for the order selection filter in your BF5 or a BF10. The 10 nm bandpass is 100 Angstroms, and you need a ~ 6 Angstrom bandpass filter for this purpose. But if you're looking to replace a failed ("rusted") induced transmission filter (ITF), one of these combined with a KG3 or KG5 filter would be just the ticket: https://www.andovercorp.com/products/co ... bing-type/

Another suitable replacement (if he ever returns from his bike ride ;-) would be Olviver Smie's IR blocked KG3 filter - but his website appears to have disappeared and I don't know when it will be back up... Another replacement option for a failed ITF would be the Maier Photonics filter specifically made for this: http://maierphotonics.com/656bandpassfilter.aspx

Diagonally parked in a parallel universe.

Curiosity is the father of knowledge; uncertainty is the mother of wisdom.

Thanks,Bob,for your reply. I have a new PST DS and wanted to somehow replace the blocking filter,not the ITF, to get more space around the suns image visually, and not have to buy the Coronado bf10 for $500. Just trolling the waters to see if this can be done less expensively.
Best,
Robert

Andover makes the BF for Daystar Quark (656FS02-12.5), it is 12.5mm diameter and cost $157 for one piece. I have replaced it with a 25mm diameter one (656FS02-25) and use it with TV 4xPowerMate to DS the LUNT50 etalon with Quark. The specification of the filter is 656.3nm Bandpass Filter, FWHM 1nm, 12.5mm dia.

Hello,Frank-
I am very interested in replacing the 5mm PST BF with either the 12.5mm or 25mm from Andover as well! I have the newer PST purchased 3months ago,but want to go the same route you did. Do you have the newer PST that is glued and was it any trouble getting it unscrewed from the ITF filter housing? How do you get the 5mm BF out of the housing and how /where does the 12.5 or 25 mm install? Is there a chance of breakage? Please help.

Robert,
Replacing the 5mm PST filter would require some major surgery to the eyepiece holder - to redrill the BF filter area to accept the larger filter.
I question the benefit of this change over in the basic PST.

Hi Robert,
I bought my PST recently (last week)too and it wasn't difficult to unscrew the filter assembly from the aluminum block. Also the ITF and BF barrel came apart relatively easily unscrewing by hand. I needed the "BOA constructor" tool only to unscrew the PST etalon from the prism block, but this will be a next step of my modification when the PST adapter arrive. I am using the 25mm diameter Andover filter and it comes in an aluminum protecting ring. I've added few layers of Scotch Aluminum tape to get the same diameter as the original Lumicon 1.25" filter was in its original barrel. Placed the Andover filter into the Lumicon filter barrel, secured with the retaining ring and mounted to a 1.25" nose-piece of my 9mm wide angle eyepiece . I've replaced the BF barrel with an 1.25"eyepiece holder from an old Celestron 1.25" diagonal which had the same thread as the BF barrel. This way I didn't modify the original PST 5mm BF and its holder.

Andover makes the BF for Daystar Quark (656FS02-12.5), it is 12.5mm diameter and cost $157 for one piece. I have replaced it with a 25mm diameter one (656FS02-25) and use it with TV 4xPowerMate to DS the LUNT50 etalon with Quark. The specification of the filter is 656.3nm Bandpass Filter, FWHM 1nm, 12.5mm dia.

Frank

It doesn't work, the 10A FWHM is too large for the finesse of an air spaced etalon. Tried it, you see faint proms and that's it.
There is no cheap alternative to the BF of Coronado and Lunt. I looked for a long time, I have contact being in optics, and no, no way.
Unless you are willing to pay a full production batch at Barr, and even in that case it will be no cheaper than out the shelf